The long term objective of this proposal is to develop a commercial vaccine for the prophylactic treatment of sexually transmitted Chlamydia trachomatis. Parenteral or oral delivery of free antigen does not protect against genital infection and therefore development of an antigen delivery method that induces a protective local immune response is crucial. Thus, the immediate focus of this proposal is to evaluate the long term local (vaginal) immune response after oral delivery in microcapsules or rectal delivery. Major emphasis will be placed on the evaluation of a vaccine based on the major outer membrane protein (MOMP) which is extensively exposed on the surface of elementary bodies (EB) and is known to elicit protective antibodies. This antigen will be purified, microencapsulated in poly-DL-lactide-co-glycolide microcapsules and delivered orally, or delivered intrarectally as free antigen. In these studies the mouse pneumonitis model of salpingitis will be used, to allow accurate, cost effective analysis of the immune response. If significant enhancement of the immune response (IgA and IgG) is observed in phase I, the studies will be expanded in phase II to include evaluation of the protective response and any associated immunopathology.